1. Field of the Invention
The present invention relates to a circuit breaker having tripping test function, and especially relates to a circuit breaker having a detachable tripping tester to be used for not only a tripping tester but also a remote controller for manually tripping the circuit breaker.
2. Description of the Prior Art
A conventional circuit breaker having tripping test function, for example, shown in the U.S. Pat. No. 4,873,603 is described referring to FIG. 3. FIG. 3 is a circuit diagram showing the conventional circuit breaker having tripping test function.
In FIG. 3, a connector 11 for testing operation has terminals 11a, 11b, 11c and 11d. The terminal 11a is connected to a negative terminal 5d of an electric power circuit 500. The terminal 11b is connected to the anode of a diode 12 which is for preventing reverse current to the terminals. And the cathode of the diode 12 is connected to a positive terminal 30a of a rectifying circuit 30. The terminal 11c is connected to a first test signal generating circuit 13 and the terminal 11d is connected to a second test signal generating circuit 14.
Terminals 15a, 15b, 15c and 15d are disconnectably connected to the terminals 11a, 11b, 11c and 11d, respectively. The terminal 15a is connected to the negative electrode of a D.C. power source 16. Other terminals 15b, 15c and 15d are respectively connected to switches 17a, 17b and 17c. And the switches 17a, 17b and 17c are connected to the positive electrode of the D.C. power source 16.
Tripping test operation of the above-mentioned conventional circuit breaker is described.
At first, the terminals 15a, 15b, 15c and 15d are connected to the contacts 11a, 11b, 11c and 11d of the connector 11, respectively.
Under the condition that the load break contact 201 is opened and any current does not flow on the A.C. power line 1, when the switch 17a is closed, a predetermined voltage, for example, 24 V is applied to the electric power circuit 500 from the outer D.C. power source 16, and a direct current (D.C.) flows on the electric power circuit 500.
Under the above-mentioned condition, when the switch 17b is closed, a switch 18 is turned to a first D.C. power source 19 by the output of the first test signal generating circuit 13. The voltage from the first D.C. power source 19 is applied to the positive input terminal of a differential amplifier 60 as an input signal and the output signal of the differential amplifier 60 is applied to a time delay circuit 70. Hereupon, since the level of the output signal of the differential amplifier 60 is high, an instant time tripping circuit 230 issues an output in the instant time tripping region as an output of the time delay circuit 70.
On the contrary, when the switch 17c is closed instead of the switch 17b, a switch 22 is turned to a second D.C. power source 20 by the output of the second test signal generating circuit 14. The voltage from the second D.C. power source 20 is applied to the positive input terminal of a differential amplifier 61 as an input signal. And the output signal of the differential amplifier 61 is applied to the time delay circuit 70. Hereupon, since the level of the output signal of the differential amplifier 61 is relatively lower than that of the differential amplifier 60, the long time tripping circuit 170 issues an output of a long time tripping region as an output of the time delay circuit 70.
As is obvious from the above-mentioned configuration, the conventional testing of the instant time tripping characteristic and the long time tripping characteristic in the state of connection of the circuit breaker actually to the power line is executed by following sequential steps of: connecting the terminals 15a, 15b, 15c and 15d to the contacts 11a, 11b, 11c and 11d of the connector 11 respectively for testing operation and turning on the switch 17; supplying the voltage of the D.C. power source 16 to the electric power circuit 500; closing the switch 17b or 17c; turning the switch 18 or 22 to be connected to the D.C. power source 19 or 20 by the output of the first or second test signal generating circuit 13 or 14; and applying the output voltage of the first or second D.C. power source 19 or 20 as a quasi input signal to the differential amplifier 60 or 61.
Besides, a solid state circuit is used as a control circuit of the circuit breaker and it is known that the solid state circuit is reliable. Accordingly, when the solid state circuit is adopted as a control circuit of the conventional circuit shown in FIG. 3, testing relatively often is necessary only for mechanical operation of the tripping.
The conventional circuit breaker having tripping test function comprises the circuit testing function performed by configuration of the test signal generating circuits 13 and 14, the D.C. power source 19 and 20 and the switches 18 and 22 for testing an instant time tripping operation and a long time or a short time tripping operation. Therefore, the complexity and the expensiveness of the control circuit of the conventional circuit breaker shown in FIG. 3 become its disadvantage. Furthermore, the disconnectable unit consisting of the D.C. power source 16, the switches 17a-17c and the terminals 15a-15d are exclusively for the circuit of FIG. 3, and the unit can not be used in another circuit breaker having different constitution from the circuit shown in FIG. 3.